Use the results of Exercises 1.28 and 1.29 to create a plot that illustrates the interaction evident from the data. Use the plot in Figure in Example 1.3 as a guide. Could the type of information found in Exercises 1.28, 1.29, and 1.30 have been found in an observational study in which there was no control on injection velocity and mold temperature by the analyst? Explain why or whynot.

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2000 Chemical Corrosion Coating 1000 Uncoated 20% 80% Humidity Aver9 Corroaion